<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        
        body {
            padding: 100px;
        }
        
        textarea {
            width: 200px;
            height: 100px;
            border: 1px solid pink;
            outline: none;
            resize: none;
        }
        
        ul {
            margin-top: 50px;
        }
        
        li {
            width: 300px;
            padding: 5px;
            background-color: rgb(245, 209, 243);
            color: red;
            font-size: 14px;
            margin: 15px 0;
        }
    </style>
</head>

<body>
    <textarea name="" id=""></textarea>
    <button>发布</button>
    <ul>

    </ul>
    <script>
        var btn = document.querySelector("button");
        var text = btn.previousElementSibling;
        var ul = btn.nextElementSibling;
        btn.onclick = function() {
            if (text.value == "") {
                alert("您没有输入内容");
            } else {
                var li = document.createElement("li");
                li.innerHTML = text.value;
                ul.insertBefore(li, ul.children[0]);
                alert("发布成功");
            }
            text.value = "";
        }
    </script>
</body>

</html>